N-Acetylcysteine Helpful for Eye Disorder
Oral supplementation with N-acetylcysteine (NAC) may be beneficial for individuals with chronic posterior blepharitis, a common inflammatory condition of the inner eyelid, according to a recent report in Cornea (2002;21:164–8). In this study, 40 individuals with chronic posterior blepharitis were randomly assigned to receive standard therapy, either alone (control group) or in combination with NAC (100 mg three times per day for eight weeks). Standard therapy consisted of topical steroids and antibiotics, warm compresses to the eyelids twice a day, and the use of artificial tears.
Compared with the control group, the group receiving NAC had a statistically significant improvement on tests that assess the structure and integrity of the tear film. Although the results were considered preliminary, these findings suggest that NAC could provide relief for individuals with this persistent and difficult-to-treat condition.
Chronic posterior blepharitis results from an abnormality of the meibomian glands of the inner eyelid that play a role in the manufacturing of tears. In some cases, it is caused by a skin disorder (either rosacea or seborrheic dermatitis). Symptoms may include burning in the eye, excessive tearing or dryness, itching, or redness of the eye. Although proper hygiene and appropriate medical treatment can help control the condition, it rarely goes away completely and often becomes progressively worse.
Scientists have theorized that the abnormality of the tear film that occurs in people with blepharitis may be a result of oxidation damage of certain key molecules produced by the meibomian glands. These molecules (phosphatidylethanolamine and sphingomyelin) contribute to the structural integrity of the oily layer of tear film. If there is a deficiency of these molecules because of excessive oxidation, the tear film may become defective, resulting in increased evaporation of tears and dryness and irritation of the eyes.
NAC is a component of glutathione, a potent antioxidant, and supplementation with NAC has been shown to increase glutathione levels in various tissues of the body. It is possible that NAC protects the tear film by increasing glutathione levels in the eye, thereby preventing the oxidation of phosphatidylethanolamine and sphingomyelin.
The amount of NAC used in the new study (300 mg per day) is half the amount used in the treatment of chronic bronchitis. Although 600 mg per day has caused intestinal symptoms, headaches, dizziness, or other side effects in as many as 20% of the participants in some studies, the smaller amount used in the new study was generally well tolerated. Additional research is needed to determine whether NAC will have a positive impact on the long-term outcome of this chronic, recurring eye disorder.
Alan R. Gaby, MD, an expert in nutritional therapies, testified to the White House Commission on CAM upon request in December 2001. Dr. Gaby served as a member of the Ad-Hoc Advisory Panel of the National Institutes of Health Office of Alternative Medicine. He is the author of Preventing and Reversing Osteoporosis (Prima, 1994), and co-author of The Natural Pharmacy, 2nd Edition (Healthnotes, Prima, 1999), the A–Z Guide to Drug-Herb-Vitamin Interactions (Healthnotes, Prima, 1999), Clinical Essentials Volume 1 and 2 (Healthnotes, 2000), and The Patient’s Book of Natural Healing (Prima, 1999). A former professor at Bastyr University of Natural Health Sciences, in Kenmore, WA, where he served as the Endowed Professor of Nutrition, Dr. Gaby is the Chief Medical Editor for Healthnotes, Inc.
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